Solution: Add Strings

Discover how to add two non-negative integers represented as strings without converting them directly into integers. Understand a step-by-step algorithm that processes digits from right to left, simulating manual addition with carry handling. This lesson helps you implement a solution with linear time and space complexity, enhancing your skills in handling string-based numeric problems efficiently.

We'll cover the following...

Statement
Solution
- Time complexity
- Space complexity

Statement

Given two non-negative integers, num1 and num2, represented as strings, return the sum of num1 and num2 as a string.

You must not use any built-in library for handling large integers (such as BigInteger) or directly convert the inputs to integers.

Constraints:

$1 \leq$ num1.length, num2.length $\leq 10^3$
num1 and num2 consist of only digits.
num1 and num2 don’t have any leading zeros except for the zero itself.

Solution

The problem requires adding two non-negative integers represented as strings without directly converting them into numeric types or using built-in big integer operations. This means that if num1 = “ $284$ ” and num2 = “ $150$ ”, then while we can’t directly convert “ ...